The present invention relates to a motor drive device and a motor system and relates to, for example, a technology for detecting the position of a sensor-less motor.
In Japanese Unexamined Patent Application Publication No. 2003-111485, a motor drive control circuit which is equipped with a current control loop which controls motor currents and a PLL control loop which determines a motor electric-conduction timing is indicated. In order to generate the electric-conduction timing which is synchronous with a back electromotive voltage (BEMF (back electromotive force)) by using the PLL control loop, a mask term (a non-electric-conduction term) which reflects the electric-conduction timing concerned is provided in a predetermined phase. The PLL control loop detects a zero-crossing timing of the back electromotive voltage while observing the back electromotive voltage of the predetermined phase in the mask term and updates the conduction timing in such a manner that the zero-crossing timing concerned is maintained at the center of the mask term.
In Japanese Unexamined Patent Application Publication No. 2017-85799, a motor drive device which drives a three-phase motor using sine waves is indicated. The motor drive device concerned partitions one period (an electrical angle of 360 deg) of the sine wave into respective 60-deg terms, fixes a terminal voltage of one phase in three phases to a power supply voltage or a ground power supply voltage in each term and controls terminal voltages of the remaining two phases with PWM signals.